1. Field of the Invention
The present invention relates to an internal combustion engine and, more particularly, to an internal combustion engine with multiple cylinders with valves that can be sequentially controllable.
2. Description of the Related Art
Some internal combustion engines include valve drive devices that are configured to sequentially control the open periods and lift amounts of intake and exhaust valves. In one example of this kind of valve drive device includes a camshaft, which drives a swing cam supported for swing movement. The swing cam actuates an intake valve or an exhaust valve between open and close positions. A center of the swing movement of the swing cam is variable. By varying the center of the swing movement, the open period and the lift amount of the valve can be sequentially changed.
In order to improve fuel consumption, an internal combustion engine can operate in the so-called “cylinder suspended mode”. In such a mode, operation of a part of cylinder groups is suspended in a low load range. Japanese Patent Application JP-A-2004-316571 discloses an example of an engine that can operate in the cylinder suspended mode. The disclosed engine also includes a valve drive device by which the open period and the lift amount of respective valves are sequentially varied.
In the engine described in JP-A-2004-316571, the cylinders are divided into multiple cylinder groups each having a control shaft so that valve lift amounts can be controllable in every cylinder group. To suspend cylinder operation, the valve lift amount of a part of the cylinder groups can be brought to zero in a predetermined operational range.